Tonight I added some new Brake lines. The old ones looked original and very brittle. The old ones had a funky fitting to go through a bulkhead, but I replaced them with a standard AN832-4D union and nut which works much better and allows for standard fittings on the lines.
Slowing working on the Cleveland brakes. Sent off the brake lines to get rebuilt and while they are gone I’m working on the calipers.
I had bead blasted the outsides and cleaned them well, but because the aircraft had sat since 1983, there was residue of the O-ring on the bore of the caliper.
I used some X-50 anti-corrosion spray and a scotchbrite to clean that area up. In the picture below you can just see that ring in the bore of the caliper on the Left and how clean the one of the right is.
Aslo found out Univair sent me the wrong -O-ring for the Piston.
Well, this weekend I wanted to get the tailwheel built up and mounted on the airframe so I can roll the darn thing around. Well as I gathered all the pieces together and started a final inspection, I noticed the Scott 3200 wheel bearings were pitted.
Next comes the research to replace them. The Bearings are Timken A4050’s with a race A4138. Looking at the regular places like Univair, Aircraft Spruce and others, these bearings are very costly considering their size. To get the Bearings, races and dust covers is over $270.
If you look up the timken A4050 on its own, you can find the bearing for MUCH less, like $40 for two bearing and race sets!
So now you are asking why? Why are the SAME bearings 1o times more expensive from the Aviation parts houses? Well I found an interesting post on this McFarlane site stating that the Aviation grade of the A4050 actually has a part number A4050-20629. https://www.mcfarlaneaviation.com/products/product/A4050/
You can see that the A4050-20629 has the FAA/PMA stamp and appears to be a black roller cage.
So I started re-building the Scott 3200 Tailwheel, refinishing the spring and such. I have the pictures of when I took the tailwheel apart and I was going to reinstall the same way until I read something in the 3200 manual that made me question something.
My original setup had 4 grade 5 bolts holding the leaf spring to the fuselage, but the 3200 manual mentioned two U-bolts. I went to the Univair site and verified the same.
So when you re-install your tailwheel ensure you have the U-bolts.
Planning on blasting the pedals, but not the torque tubes as they are two piece and lubricated so they move to actuate the brakes. Don’t want any blast media in there. I will be painting the tubes once cleaned. the bearings are in decent shape and I will know more after the cleanup, but I may have to take the advice from the site above and replace with a similar bearing.